Value Change Event Listener
Value Change Listener can be implemented in 2
ways. If you use the first one then it will limit you to use only one listener
for the component but second way permits you to include more than one listeners.
1. Using "valueChangeListener" attribute of the
component tag
<h:selectOneMenu id="songList"
value="#{ValueChangeBean.selectedSong}" valueChangeListener="#{ValueChangeBean.processMyValueChange}" immediate="true" onchange="this.form.submit()">
<f:selectItems value="#{ValueChangeBean.songList}"/>
</h:selectOneMenu> |
Sample Code for processMyValueChange method
in "ActionBean":
public void processMyValueChange(ValueChangeEvent vce){
songvalue = (String) vce.getNewValue();
setSongDetail((String)detail.get(songvalue));
/*Render the response*/
FacesContext.getCurrentInstance().renderResponse();
} |
2. Using <f:valueChangeListener /> tag
The ValueChangeListener interface must be implemented
to capture an ValueChangeEvent. This interface provides processValueChange()
method which is called when the ValueChangeEvent action observed by this
listener occurs. So processValueChange() method should be implemented for the
value change event listeners.
processValueChange method signature:
| public void
processValueChange(ValueChangeEvent event) throws
AbortProcessingException |
For example:(In JSP)
<h:inputText id="name" immediate="true" onchange="this.form.submit()" required="true">
<f:valueChangeListener type="roseindia.MyValueChangeBean" />
</h:inputText> |
The code for MyValueChangeBean.java:
package roseindia;
import java.util.*;
import javax.faces.event.*;
import javax.faces.context.FacesContext;
public class MyValueChangeBean extends Object implements ValueChangeListener {
public void processValueChange(ValueChangeEvent event) throws AbortProcessingException
{
if (null != event.getNewValue()) {
FacesContext.getCurrentInstance().getExternalContext().getSessionMap().put("name", event.getNewValue());
}
}
} |
Download
code for all examples
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